Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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860
FXUS64 KHGX 101034
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
434 AM CST Sat Dec 10 2016

.DISCUSSION...
Surface high pressure was located over the Ohio River valley this
morning. The high continues to ridge into SE TX but will begin to
lose it`s influence as it moves east. NE winds will become east
and eventually SE as the surface high shifts east and low pressure
develops over the western high plains. Today will start on the
cold side once again but weak warm air advection should allow for
slightly warmer temperatures this afternoon. Clouds are expected
to thicken and overspread most of the region by this afternoon.
Moisture levels increase tonight through SUnday night and fcst
soundings saturate from the surface to around 850 mb. Should start
to get some showers in the warm air advection regime coupled with
a very weak upper level disturbance tonight into Sunday. Will
maintain the chance PoPs currently in the forecast. Temperatures
will likely remain steady or slowly warm tonight into Sunday
morning. A weak cool front will approach SE TX Sunday night and
this feature will serve as focus for additional showers. The front
will stall near the coast Monday afternoon focusing the higher
rain chances mainly in the coastal counties. The Monday front will
will begin to retreat slowly north on Tuesday and act a bit like a
warm front. Moisture levels increase as does warming at 850 mb.
This produces a bit of a cap over most of the region. That said,
fcst soundings show a saturated layer extending up to 850 mb and
PW values near 1.30 inches. GFS soundings show the cap eroding in
the late afternoon. Not sure this will occur as expected cloud
cover should limit heating which should allow the cap to hold.
Will continue to carry lowish PoPs for Tuesday for weak WAA
showers.

A variety of differing model solutions to choose from for the
middle and latter half of next week. Increased warming at 850 mb
would suggest some warming near the sfc and went slight above
blended guidance on Tues/Wed with max temps possibly warming into
the mid 70`s central and southern zones. A weak cold front will
move across SE TX Weds night and colder temps will filter into SE
TX for Thursday. GFS hinting at weak isentropic upglide and some
light rain while the ECMWF is drier. The upper pattern is not
showing much amplification so feel isentropic upglide will be too
weak to generate much in the way of precip. Will maintain the 20
PoPs currently in the grids.

Models having a very difficult time with the timing and intensity
of the next cold front. Both the ECMWF and GFS are trending
significantly warmer for the end of the week into next weekend.
Ensemble guidance shows a temperature range between 75 and 55
degrees for high temperatures. Wanted to go with the warmer
temperatures as the pattern just doesn`t look favorable for a big
push of colder air. Started to trend the temps warmer but am a
little nervous to go too warm only to have the models flip back to
a strong front. Basically, just split the differences and took the
avg ensemble temperature value for Fri/SAT. A lot of uncertainty
toward next weekend with regard to rain chances and temperatures.
43

&&

.MARINE...
The moderate easterly winds were slowly diminishing. Caution
conditions due to winds and seas over the 20 to 60 nm Gulf waters
will subside below criteria by mid morning. The reprise will be
short lived as moderate onshore winds will develop by late this
evening with caution conditions returning over the offshore waters.
These will persist through Sunday.

The approach of a weak front on Monday should lead to lowering winds
and seas over the Gulf waters. A stronger front is expected to move
off the coast sometime Wednesday night or early Thursday morning.

40

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      55  49  72  60  69 /  10  30  30  10  10
Houston (IAH)              57  50  74  65  75 /  10  20  30  30  20
Galveston (GLS)            60  58  71  66  70 /  10  10  20  30  40

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 9 AM CST this morning
     for the following zones: Waters from Freeport to the
     Matagorda Ship Channel from 20 to 60 NM...Waters from High
     Island to Freeport from 20 to 60 NM.

&&

$$



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